1. Field of the Invention
The present invention relates to an electrolytic solution including an electrolyte salt and a battery using the electrolytic solution.
2. Description of the Related Art
In recent years, a large number of portable electronic devices such as camcorders, digital still cameras, cellular phones, personal digital assistances and laptop computers have been emerged, and an attempt to reduce the size and the weight of them has been made. Accordingly, the research and development of batteries, specifically secondary batteries as portable power sources for the electronic devices for improving an energy density have been actively promoted. Among them, a lithium-ion secondary battery using a carbon material for an anode, lithium (Li) for a cathode and a carbonate for an electrolytic solution has been widely put to practical use, because the lithium-ion secondary battery can obtain a larger energy density than a lead-acid battery and a nickel-cadmium battery in related arts.
Moreover, recently as the performance of portable electronic devices is enhanced, further improvement in capacity is desired, and it is considered to use tin (Sn) or silicon (Si) as an anode active material instead of a carbon material. The theoretical capacity of tin is 994 mAh/g, the theoretical capacity of silicon is 4199 mAh/g, so the theoretical capacities of tin and silicon are much larger than the theoretical capacity of graphite, 372 mAh/g, so an increase in capacity can be expected. In particular, it has been reported that in an anode formed by forming a thin film of tin or silicon on a current collector, an anode active material is not pulverized by insertion and extraction of lithium and a relatively large discharge capacity can be maintained (for example, refer to the pamphlet of International Publication No. WO01/031724).
Further, as a secondary battery capable of obtaining a high energy density, there is a lithium metal secondary battery using lithium metal for an anode and using only precipitation and dissolution reactions of lithium metal for an anode reaction. The lithium metal has a large theoretical electrochemical equivalent of 2054 mAh/cm3, which is 2.5 times larger than that of graphite, so the lithium metal secondary battery holds promise of improving the capacity. A large number of researchers have been conducting research and development aimed at putting the lithium metal secondary battery to practical use (for example, refer to “Lithium Batteries” Edited by Jean-Paul Gabano, Academic Press, 1983, London, N.Y.).